The invention relates to a feeding device of an agricultural machine such as a forage harvester wherein the feeding device includes a gear transmission to which is coupled either a hydraulically or electrically driven motor.
DE-C2-28 19 200 shows an ensilage harvester having a feeding device that includes several rolls mounted on parallel axes for feeding harvested crop material to a cutterhead. The feed rolls are grouped in two sets of two and are driven via a spur gear train, with each set of rolls being driven by a hydraulic motor. Both hydraulic motors are fed by a variable displacement hydraulic pump, and depending on the displacement, may deliver a slower or faster initial speed, whereby the length of the cut of the crop material is varied. Such a drive requires the hydraulic pump and motors to be of high efficiency, and, because of the volume of fluid required to be pumped for chopping to the capacity of the machine, for there to be a cooler for the hydraulic fluid.
It is also known to drive the feed rolls of the feeding device in a purely mechanical manner by way of intermediate gearing that may be selectively shifted or with replaceable gears so as to achieve different drive speeds of the feed rolls in order to vary the length of cut of the crop material delivered to the cutterhead.
The underlying problem addressed by the invention is that, in the known driving arrangements for the feeding device, an easy, infinite adjustment of the crop material delivery speed, and, hence, the cutting length, is not possible without the expense of relatively high capacity, high efficiency hydrostatic transmissions.